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Discussion Starter #1 (Edited)
Got my 2007 Solstice GXP Manual back in March. Only one owner and he always used Autolite XP 5263 Plugs. Once Spring came, once in awhile I would get the misfire code, so I did a lot of reading on the forms. Everyone seems to use the AC 41-108s. So I bought those and also Bosch Platinum IR Fusion 4515 Plugs.

Drove for a month of the AC 41-108s, seemed to work alright but the acceleration and power seemed to lack. So I put in the Bosch Plugs and WOW. I could feel the difference and the car took off even faster then ever. The misfire code has not come on since the Autolite Plugs and the car is running amazing. Btw used the same fuel grade 91 No Ethanol and same gas station the whole time.

Just surprised no one has tried these out but me. They are certainly worth a mention and I have been using the Bosch ever since. Hope this helps our group out!

Safe Motoring Everyone!
 

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A few questions come to mind. Are you tuned? Next question.... Are these plugs the exact same? Gapped? Same length so one isn't sitting further in the motor then the other? Final question, if you are tuned, how much boost are you pushing? If they are "hotter" plugs, they are usually sitting a little different. And you must be careful with "hotter" plugs in these cars...Bad, expensive things can happen quickly.

Let me elaborate. IMSMC we had someone running a much "hotter" plug. The engine ran great for about 2k miles. And then he burned a whole in the piston. You have no clue what the temp is inside the combustion chamber and the LNF is extremely delicate and doesn't like a whole lotta change...ie hotter plugs. If you're getting that much more performance...be very careful. The stock piston heads are very thin on these motors and they don't take a lot of extra heat very well....just warning you.
 

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Discussion Starter #3
I’m currently not running any tune. They come already gapped and there isn’t a way to gap them. That’s what took the longest on the research, was to find the right plug. Had to cross reference plug after plug just to be 100% sure. Bosch plug code for them are HGR8MQI. So the “8” is how hot and cold they run. They can go as hot as 13. I attached the chart to the post.
 

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Were they pre-gapped or what gap did you use? How did you come up with that plug number... My charts shows 96301 and 9723.
 

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Discussion Starter #6
Were they pre-gapped or what gap did you use? How did you come up with that plug number... My charts shows 96301 and 9723.
They were gapped already. You are unable to gab these ones. I cross referenced BOSCH PLATINUM IRIDIUM FUSION # 4515 HGR8MQI and they showed the Autolite XP 5364 Denso 5339 and Denso ITV20. Which all work with the Solstice GXP, you can also cross reference the Autolite XP 5364 and our AC 41-108 show up.
 

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A few questions come to mind. Are you tuned? Next question.... Are these plugs the exact same? Gapped?
So if two plugs are the same heat rating and size - how important is a difference in gap? Say from a .9 to a 1.0?
 

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Discussion Starter #8 (Edited)
A few questions come to mind. Are you tuned? Next question.... Are these plugs the exact same? Gapped?
So if two plugs are the same heat rating and size - how important is a difference in gap? Say from a .9 to a 1.0?

I am not too sure man. I know that a larger gap then what the manual recommends makes your ignition coils work a lot hard and you can go thru them a lot quicker.

I read a lot of other forms on here where some had theirs at .035 all the way down to .028 .They said the .028 was the best gap he tried.

I was just excited to share with everyone a different Spark Plug that seems to work better then stock. Because it really seemed like our Solstices couldn’t use other plugs.
 

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I read somewhere that a bigger gap caused problems with high boost cars...
 

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The Bosch site list the 9723 with a .9mm (.35") gap as the preferred plug for our GXPs.
 

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Discussion Starter #14
Here is a picture of the Bosch Platinum Fusion IR 4515.
The Bosch website shows the 4515 as 'discontinued'
Yeah, I believe that. Because they are getting harder and harder to find. I used the Bosch Platinum Fusion IR in my Jeep Wrangler year’s back, just after they stopped making them. Those worked GREAT for my Wrangler too come to think of it.....
 

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Ive used hundrad sets of the bosche platinum plugs. I put the denso iridium plugs in my solstice because they were cheeper......and I wanted to try them. Ive put well over 100000 miles on bosch plat plugs with no issues, there especialy good for performance app's, and oh so sweet on old stuff that had a habbet of fouling plugs due to big carbs or cam or tune off.Ive never had one foul or mis fire. the only other thing I dont run them in is my 2 stroke dirt bike(yz250). they are awesome with lackluster ignition systems too as they fire good with less voltage than a std plug.
 

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If the gap is too big on a higher boost car, the boost blows out the spark. And IMSMC, the 4 prongs cause issues in our cars. I can't remember if it's with the coils or too much heat. I asked this question many years ago when I first became a member and was told not to use 4 prong plugs.
 

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FWIW, I am a long time NGK fan. I switched from Champion early in my racing career and also used their plugs on all my street cars.

You probably haven't seen a lot of spark plug talk here because the stock plugs seem to work quite well in our cars. I expect that I will likely replace my plugs in the GXP with factory original plugs when the time comes - if it ain't broken....

The NGK OEM replacement is ILTR5D if anyone is interested in trying them. The NGK list indicates that it is an OEM equivalent and has a 100K replacement interval. They also offer an iridium plug and a 'G-power' plug, whatever that might be.
 

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FWIW, I am a long time NGK fan. I switched from Champion early in my racing career and also used their plugs on all my street cars.

You probably haven't seen a lot of spark plug talk here because the stock plugs seem to work quite well in our cars. I expect that I will likely replace my plugs in the GXP with factory original plugs when the time comes - if it ain't broken....

The NGK OEM replacement is ILTR5D if anyone is interested in trying them. The NGK list indicates that it is an OEM equivalent and has a 100K replacement interval. They also offer an iridium plug and a 'G-power' plug, whatever that might be.
I use the OEMs also with no problems. As an aside, the so called "pre gapped" plugs can be gapped just like any other single anode plug. Only difference is that you have to stay away from the cathode, which is brittle and easily broken. You can buy a gapping tool especially for these plugs at any parts store for about three bucks. If you use a pre gapped plug with a wider gap, it will work but it causes the coils to work harder the push the spark across the gap, particularly in higher compression engines.

Bill.
 

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Ive thrown away tomany ngk's to put them in any thing unless they arengk iridum or plattys. but the price was just a bit high for me to get them for my solstice....nippon denso has a much better price.( I think I get the set of iridum for about $17 including shipping) many people dont know about the big spark plug price fixing scheem as well as brake parts scheem that got some oe supplier and car company's some big fines..really big fines,bosche was one of them ,it was a massive issue with japan&euro cars and price fixing to the manufactures...witch trickled down to us. a $6 spark plug the manufactures were paying 20 for..isant much untill you add up all the cars. some companys that were not part of the scam, were part of the investagation to help nail the others. that was about 3 years ago as I recall, and some plug prices have fallen. I changed mine to the denso because the AC were all rusted.not good.
 

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Discussion Starter #20
Just ordered some Brisk RR15BSXC Premium EVO. Suppose to be the best spark plugs made for racing. Thought I’d give them a try and tell everyone how they are working.

They won’t be here till next week. I am really looking forward to these! No gapping , 2 sparks in one plug! Suppose to really make the engine perform.
 
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